A fused silica ceramic body is practical and advantageous for a number of diverse applications. Such a body is rendered all the more useful by the autogenic generation of a thin vitrified silica layer on an inner surface of such a body to prevent moisture and other fluids from penetrating through the wall of the body. Optimal performance of such a fused silica body with a vitrified layer requires that the vitrified layer be relatively thin, uniform, and of constant thickness within a relatively tight tolerance. The desired consistency of layer properties over the entire layer and repeatability over different production units of such a body would be expensive and difficult to achieve with a manual vitrification process.